For over fifty years heavy haul railroads have used a variety of methods to reduce friction between the locomotive and railcar wheel flanges and the gauge face of the rail with which it comes in contact. Railroads and transits have realized they can save substantial amounts of money in lowered maintenance and equipment replacements if lubrication is applied. Several methods have been used including one method wherein hundreds of wayside lubricators eject hydrocarbon petroleum based lubricants onto the gauge face of the rail as the train travels through a curve. A second method for applying lubricant has been to use track inspection trucks to spray petroleum or synthetic grease onto the gauge face of the track at the inspection truck goes through a curve. A third method is to apply lubricant to the wheel flange of the locomotive whereupon the lubricant gets transferred from the wheel flange of the locomotive to the wheel flange of railcars. Lubricant is then passed back through the train as successive wheels come in contact with the rail and pick up some of the lubricant.
These types of lubrication are typically accomplished by spray devices that squirt small amounts of lubricating oil onto wheel flanges. There are inherent problems with the above-described methods of applying lubricant. First, sprayed oil has a tendency to migrate to the tread of the wheel, making it more difficult for the train to stop. Also, grease and oil on top of the rail can cause the train wheels to slip inhibiting the ability of the brakes of the train to slow or stop the train. In addition, grease and oil on top of the rail can make it difficult for the train to gain traction from a stopped position or when climbing an incline. Secondly, to keep oil spray devices in working order has required excessive maintenance time and expense.
An alternative method for overcoming problems with spraying oil onto the wheel flange of the locomotive or railcar has been to use a solid lubricant stick or rod. The stick or rod is inserted into a tube that is then applied by various mechanical means to the flanges of the wheel of a locomotive or railcar.
Prior art solid lubricants also have several inherent problems. First, prior art lubricant sticks contain graphite or molybdenum powders because of their anti-wear properties. These prior art molybdenum disulfide compound sticks were made without polymers whereby the molybdenum disulfide was smashed together in a foil wrapper. However, this made the lubricant stick very hard and brittle, so that they could not withstand a rugged locomotive or railcar environment and the sticks would break or disappear.
Prior art solid lubricant stick compositions also have used polymeric carriers to provide durability, but have also included materials that do not provide extreme pressure anti-wear protection or are potentially hazardous to the environment. In some prior art, the sticks have promoted the ability to lubricate a particular wheel flange, but because they have not contained additives to withstand the extreme pressure of a locomotive or railcar flange against the track, the lubricant has not transferred throughout the train. In other prior art, the solid lubricant has lubricated throughout the train, but these formulas contain undesirable hazardous metallic powders, because of their anti-wear capabilities, but the metallic powders not only pollute the environment, but also may be hazardous to railroad workers.
U.S. Pat. No. 3,537,819 to Davis et al., discloses that the characteristics of the solid lubricant such as hardness, deposition and rigidity are dependant on the molecular weight and the amount of high molecular weight polyethylene that is used.
U.S. Pat. No. 3,541,011 to Davis et al., also discloses a solid lubricant whereby the characteristics of the lubricant such as hardness, deposition and rigidity are dependent on the molecular weight and on the amount used of high molecular weight polyethylene.
U.S. Pat. No. 3,729,415 to Davis et al., discloses a combination of polyethylene and hydrocarbon oil in a stick lubricant that does not contain extreme anti-wear materials to prevent excessive wear.
U.S. Pat. No. 4,915,856 to Jamison discloses an alternative solid polymeric stick formula, which includes lead and other metallic powder in either single or co-extruded compositions. While the metallic powder offers anti-wear properties, it also can pollute the environment, such as ground water, when it drops alongside and also can present hazardous conditions for rail workers. Inclusion of metallic powders which may be considered hazardous by the E.P.A. is undesirable to railroads and transits.
In order to overcome problems inherent in the prior art there has been devised by the present invention a solid lubricant and composition useful for lubricating the flanges of locomotive wheels, railcar wheels, rail track and in applications where it is desirable to reduce friction when metal contacts metal. The solid lubricant of the present invention comprises from about twenty-five percent to about seventy percent by volume of a polymeric carrier, and in combination about five to seventy-five percent by volume of organic and inorganic extreme pressure additives, including an organic and inorganic powder lubricant and optionally a synthetic extreme pressure anti-wear liquid oil and/or an optical brightener so that the lubricant can be seen under black light conditions to allow verification that the lubricant is coating the surface to which it is applied.
In the preferred embodiment, the solid lubricant composition comprises two portions, namely a first portion and a second portion. The first portion of the lubricant stick is composed generally of the following formula one: from about twenty-five percent to about seventy percent by volume (preferably from about thirty-five percent to about thirty-nine percent) of a polymeric carrier with a relatively high melt index, such as a linear low density polyethylene, a low density polyethylene, a polyolefin or a synthetic wax; from about five percent to about seventy-five percent by volume (preferably about sixty percent) of organic and inorganic powder; from about zero percent to about twenty percent by volume (preferably about one percent to about four percent) of a synthetic extreme pressure anti-wear oil; and from about zero percent to about one percent by volume (preferably about one percent) of an optical brightener. The second portion of the lubricant stick is composed generally of the following formula two: from about twenty-five percent to about seventy percent by volume (preferably about twenty-nine percent) of linear high density polyethylene polymeric carrier with a relatively low melt index; from about five percent to about seventy-five percent by volume (preferably about sixty-five percent) of organic and inorganic powder; from about zero percent to about twenty percent by volume (preferably about five percent) of a synthetic extreme pressure anti-wear oil; and from about zero percent to about one percent by volume (preferably about one percent) of an optical brightener.
The solid lubricant of the present invention uses two distinct thermo-polymer resins with different melt flow temperatures and melt point indexes to form a two portion lubricant. The first portion of applied lubricant is rapidly penetrated into a metallic surface when lubricant is first applied to a metallic surface. The second portion of the lubricant is applied more slowly, when less is needed.
Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description wherein I have shown and described only the preferred embodiment of the invention, simply by way of illustration of the best mode contemplated by carrying out my invention. As will be realized, the invention is capable of modification in various obvious respects all without departing from the invention. Accordingly, the drawings and description of the preferred embodiment are to be regarded as illustrative in nature, and not as restrictive.